There are many applications for which precise control over the amount and/or rate at which a fluid is dispensed by a pumping apparatus is necessary. In semiconductor processing, for example, it is important to control the amount and rate at which photochemicals, such as photoresist chemicals, are applied to a semiconductor wafer. The coatings applied to semiconductor wafers during processing typically require a certain flatness and/or even thickness across the surface of the wafer that is measured in angstroms. The rates at which processing chemicals are applied (i.e., dispensed) onto the wafer have to be controlled carefully to ensure that the processing liquid is applied uniformly.
Photochemicals used in the semiconductor industry today are typically very expensive, costing as much as $1000 and up per a liter. Therefore, it is highly desirable to ensure that a minimum but adequate amount of chemical is used and that the chemical is not damaged by the pumping apparatus. Current multiple stage pumps can cause sharp pressure spikes in the liquid. Such pressure spikes and subsequent drops in pressure may be damaging to the fluid (i.e., may change the physical characteristics of the fluid unfavorably) and/or adversely affect the performance of the pumping system. Additionally, pressure spikes can lead to built up fluid pressure that may cause a dispense pump to dispense more fluid than intended or dispense the fluid in a manner that has unfavorable dynamics.
One shortcoming of prior pumps is interfacing the pump controller with other devices. The pump controller typically receives signals from a control system (e.g., other computers/tools) to receive process parameters, trigger signals or other signals and sends signals to indicate the state of a dispense cycle or other data. Many computers/manufacturing tools, however, use different physical interfaces and signaling schemes to communicate signals to and receive signals from a pump. Generally, for each input/output line, the pumping system requires one conductor leading to the pump controller. This means customizing the pump controller for a pump for the specific interface on another device to/from which the pump communicates data. In semiconductor manufacturing systems which generally use a large number of pump signals this can lead to complicated wiring leading to a single pump. Moreover, in many semiconductor manufacturing systems, there are multiple pumps stacked together, leading to a complicated array of wires leading to the pumps. Another shortcoming of prior systems was that the discrete input/output (“I/O”) lines were limited in length. There is a need for new and better ways to interface devices with the pumps. Embodiments of the invention can address this need and more.